The present invention relates to a sealing gasket for cables, in particular for electrical or optical telecommunications cables.
More precisely, the invention relates to a sealing gasket for cables, in particular optical or electrical telecommunications cables, for mounting in an inlet of a sealed box for protecting splices and containing a gas under pressure, the gasket being mounted in a tubular passage secured to the box and comprising at least one tubular cylindrical portion of constant diameter having an inner sealing portion connected thereto to bear against the periphery of the cable and to be placed towards the inside of said box.
Such a sealing gasket device is known from patent document DE-U-782 425. In that document, a gasket is mounted in conventional manner on a box, and more precisely on a support tube mounted on the box, and it is clamped by a nut or packing member screwed onto said tube and compressing it against the cable. That gasket has an outer frustoconical portion terminating in a sealing lip which is pressed against the periphery of the cable by the screwed-on nut. The gasket also has flexible inner sealing lips placed towards the inside of the box and bearing against the cable by elastic deformation.
The inner lips perform a sealing function in addition to that of the outer lip, and they are not capable on their own of providing effective sealing, given the pressure of the gas that exists inside the box.
The object of the invention is to provide an inner sealing portion which provides full sealing on its own, i.e. which does not need to be associated with an outer lip in order to provide a gasket that is effectively sealed.
To do this, according to the invention, the inner sealing portion is constituted by a tubular frustoconical portion connected to the end of said cylindrical portion and whose smaller diameter end presents an orifice of diameter smaller than the diameter of the cables to be mounted.
This arrangement presents the advantage of the gasket being reusable after the sealing assembly has been dismantled.
Furthermore, in the above-cited prior art, the inside diameter of the outer sealing lip is smaller than the outside diameter of the cable in order to apply pressure around the cable once the nut has been tightened. That gasket is therefore designed for cables of a particular diameter. In other words, each cable diameter corresponds to a particular type of gasket having dimensions that match those of the cable.
Advantageously, the invention makes it possible to use standard gaskets, a single gasket being manufactured and being suitable for mounting on a range of cables of different diameters.
In a preferred embodiment, the inner sealing portion is constituted by a tubular frustoconical portion whose smaller diameter end has an orifice of diameter smaller than the minimum diameter of cables to be mounted.
A standard gasket can be manufactured, with its end being cut to the desired inside diameter prior to being mounted on the cable, the cut diameter being slightly smaller than the diameter of the cable so as to provide good sealing pressure against the periphery of the cable.
Preferably, said frustoconical portion is provided on its outer face with annular cutting grooves that are regularly spaced apart.
These grooves make it easier to cut the gasket to the desired diameter, which is slightly smaller than the diameter of the cable which is to be mounted.
In a variant, said cylindrical portion is terminated by an outer sealing lip opposite from said frustoconical portion.
This more complex variant has the advantage of presenting better sealing ability, by combining inner sealing with outer sealing. In addition, given that in this variant the cable is supported by two spaced-apart peripheral contacts with the gasket, one inner contact and one outer contact, the gasket is not damaged by any bending of the cable. This is particularly important when a plurality of cables are being mounted using a single gasket having a plurality of bores. Under such circumstances, during mounting, the cables are subjected to bending caused by elements of the sealing assembly being turned.
The invention also provides a sealing assembly for cables, in particular for electrical or optical telecommunications cables, for mounting at the inlet of a sealed box for protecting splices and containing a gas under pressure.
In a first variant, the gasket mounted in said tubular passage with its inner sealing portion disposed towards the inside of the box is held in position by an outer cylindrical plug screwed onto the tubular passage and holding said gasket longitudinally.
In a second variant, the gasket mounted in said tubular passage with its inner sealing portion disposed towards the inside of the box has its outer sealing lip thrust peripherally against the cable by a cable-guide, itself thrust in the longitudinal direction by a nut or packing member screwed onto the tubular passage.